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Among the sometimes-overlooked nutrients in the home apple orchard, calcium is crucial in preventing disorders such as bitter pit and cork spot. Additionally, adequate calcium in the soil surrounding apple trees helps the harvested fruit store for longer periods. Feed the soil around apple trees in addition to undertaking a foliar spraying program, which is a more immediate method for getting the nutrient to calcium-stressed trees.

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Rake any mulch or debris away from the ground beneath the tree's outermost branches, extending about five feet in all directions beyond this drip line.

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Sprinkle 10 pounds of gypsum to add calcium to the soil. Concentrate on the soil containing the tree's feeder roots, from the drip line to several feet beyond the outer branches. For younger and dwarf apple trees, consult package directions, as you will likely need to use less gypsum per tree.

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Add additional layers of other amendments, if they are part of your annual feeding program. Nitrogen sources such as blood meal and phosphorus amendments like bone meal are common elements of a springtime apple tree feeding schedule.

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Work the gypsum and other amendments into the soil with a spade or hoe. Aim for a depth of 1 to 2 inches; this depth won't hurt the branches, but will help accelerate the leeching of calcium from the gypsum into the soil.

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Water the drip line area deeply, beginning the calcium-leeching process.

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Rake mulch back into place, topping old material with fresh mulch, if necessary,

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Repeat the feeding process each year in early spring.

Things You Will Need

Soil sample

Rake

Gypsum

Hoe or spade

Hose or drip irrigation system

Mulch (as needed)

Tips

Because gypsum takes at least two years to make a difference to apple trees, yearly foliar feeding of a calcium source is crucial. Calcium nitrate and calcium chloride are two common sprays used to provide calcium to trees. These foliar sprays are best used several times throughout the flowering and fruiting season.

Warning

If your soil pH is already lower than 6.2, use an alternative source of calcium instead of gypsum, such as ground eggshells or ground oyster shells. You'll need about 2 pounds per 100 square feet of drip line area.

About the Author

Ellen Douglas has written on food, gardening, education and the arts since 1992. Douglas has worked as a staff reporter for the Lakeville Journal newspaper group. Previously, she served as a communication specialist in the nonprofit field. She received her Bachelor of Arts from the University of Connecticut.